An examination of latitudinal variation in the growth rates of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea

Following a finding that a small sample of aged Dissostichus mawsoni from McMurdo Sound (76° S) fell consistently below the von Bertalanffy curves calculated predominantly from data collected between 67 and 74° S, an investigation to test for latitudinal differences in growth rates was conducted. Length-at-age of Dissostichus mawsoni was compared across five zones in a 15.5° latitudinal range (62.5°–78.0° S). Between-zone comparisons were confounded by marked differences in the age structure of catches from the northern and southern sections of the range, and by the relatively high level of variance in the length-at-age data. There is no statistically significant difference in mean growth rates of D. mawsoni between 62.5° and 75° S. However, fish between the ages of 6 and 15 years in the southernmost zone (75–78° S) are, on average, significantly smaller at age than those in the more northern zones. There were insufficient older fish in the southernmost zone to enable a comparison with other areas. Any real latitudinal differences in growth rates for relatively sedentary fish are likely to be blurred by migration between latitudes.